From: Jesse Barnes <jbarnes@engr.sgi.com>
To: Andi Kleen <ak@muc.de>
Subject: Re: Direct io on block device has performance regression on 2.6.x kernel
Date: Wed, 9 Mar 2005 15:52:41 -0800
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Cc: "Chen, Kenneth W" <kenneth.w.chen@intel.com>, linux-kernel@vger.kernel.org,
       axboe@suse.de
References: <200503092218.j29MICg26503@unix-os.sc.intel.com> <m1r7iov1ya.fsf@muc.de>
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On Wednesday, March 9, 2005 3:23 pm, Andi Kleen wrote:
> "Chen, Kenneth W" <kenneth.w.chen@intel.com> writes:
> > Just to clarify here, these data need to be taken at grain of salt. A
> > high count in _spin_unlock_* functions do not automatically points to
> > lock contention.  It's one of the blind spot syndrome with timer based
> > profile on ia64.  There are some lock contentions in 2.6 kernel that
> > we are staring at.  Please do not misinterpret the number here.
>
> Why don't you use oprofile?>? It uses NMIs and can profile "inside"
> interrupt disabled sections.

Oh, and there are other ways of doing interrupt off profiling by using the 
PMU.  q-tools can do this I think.

Jesse
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